This invention relates to a liquid film forming method wherein a liquid is applied onto a substrate to be processed so as to form a liquid film.
In spin coating method, which has been used in lithographic steps, almost all of a liquid dropped onto a substrate is discharged outside the substrate so that a film is formed from the remainder thereof, which is several percent of the liquid. Therefore, most of the dropped liquid is of no use. Since most of the liquid is discharged, an adverse effect is produced on environment. Moreover, there arises a problem that in rectangle substrates or disc-shaped substrates having a large diameter of 12 inches or more, turbulent air is generated at the circumferential portion of the substrates so that the film thickness uniformity of this portion becomes deteriorated.
As a method of applying a liquid uniformly onto the whole of a substrate without vain use of the liquid, Jpn. Pat. Appln. KOKAI Publication No. 2-220428 describes a method of dropping a Resist from many nozzles which are arranged along one line and, spraying from the back thereof, a gas or a liquid onto a film-forming surface to obtain a uniform film. Jpn. Pat. Appln. KOKAI Publication No. 6-151295 describes a technique wherein many spray nozzles are made in a rod and a resist is dropped out from them onto a substrate in order to obtain a uniform film. Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 7-321001 describes a method of using a spray head in which many spray nozzles for spraying a resist are made and moving the head relatively to a substrate to perform application.
In all of these applicators, plural dropping or spraying nozzles are arranged along one rank and they are scanned in order to obtain a uniform film. Besides application methods using a device having these nozzles, there is known a method of using a single liquid jetting-out nozzle and the nozzle is scanned over a substrate to be processed, so as to form a liquid film.
These methods have a problem that the processing time per substrate becomes long dependently on a method of handling the nozzle(s) or the use amount of a liquid gets very large.